330 ENCOPE MICHELINI. 



are only nominal species, all identical with E. occidentals ; and as the name 

 " micropora " seems to be the most appropriate, besides being the oldest, it 

 would be the best name to retain. A careful statement of the points of dif- 

 erence between E. micropora and E. emarginata will be found in the descrip- 

 tion of the Panama species, in the general descriptive part of the species. 



This species is readily distinguished from E. emarginata by the position 

 of the vertex, which is directly in front of the small posterior lunule, and is 

 not due, as is sometimes the case, to the swelling of the lip of the lunule, 

 but to a rise in the test itself. The outline resembles, at first glance, 

 more that of E. grandis, but it is more pentagonal ; the lunules are 

 frequently closed, and when closed become obliterated exteriorly in old 

 specimens; the small size of the posterior interambularral lunule is strik- 

 ing, scarcely as large as the marginal lunules ; the three anterior lunules 

 are frequently mere indentations in the margin, giving to the general outline 

 very much tin- appearance of Echinodiscus with an interainbulacral lunule 

 {PL XII'. f. -,'). The vertex as well as the mouth is nearly central; the 

 anus is placed about one third the distance from the mouth to the edge of 

 the test. The tubercles are more closely packed than on the upper part of the 

 test of E. emarginata, while the spaces filled with larger tubercles between the 

 bare avenues adjoining the ambulacra! furrows of the lower side are Barrow, 

 and the tubercles smaller than in the preceding species. It is, however, on 

 examining the interior {PL XIP. f. 4), that we are at once struck with the 

 remarkable differences to be noticed between these two species. The size 

 of the jaws, the narrow marginal band connecting the two lloors. the great 

 size of the cavity occupied by the alimentary canal, the width of the alimen- 

 tary canal, and the size of the walls separating its different convolutions, 

 contrast strikingly with the small jaws, the narrow convolutions of the 

 alimentary canal, and the great breadth of the marginal band connecting 

 the upper and lower floors of E. emarginata {PL XIP. f. ■;). 



Littoral to 1 1 fathoms. 



